The present invention relates to a suspension for supporting a head section of a disk drive stored in an information processing apparatus such as a personal or portable computer.
FIG. 8 shows a part of a hard disk drive (HDD) 1. A carriage 2 of the HDD 1 is turned around a shaft 2a by means of a motor 3 for positioning, such as a voice-coil motor. The carriage 2 is composed of a coil portion 5 located near magnets 4 of the motor 3, arms (actuator arms) 6 fixed to the coil portion 5, suspensions 7 situated on the distal end of the arms 6, heads 8 attached individually to the respective distal end portions of the suspensions 7, etc. Each head 8 can be moved to a desired track (recording surface) of a hard disk 9 by driving the carriage 2 in the aforesaid direction by means of the motor 3.
Each head 8 is provided with a slider 10, which is located in a position such that it can be opposed to the tracks of the disk 9, a transducer (not shown) held by the slider 10, etc. When the slider 10 is slightly lifted above the surface of the disk 9 as the disk 9 rotates at high speed, an air bearing is formed between the disk 9 and the slider 10.
FIGS. 9 and 10 show a prior art example of the suspension 7. This suspension 7 has a standard shape called Type 8 in the art. The suspension 7 includes a load beam 11 formed of a thin precision plate spring, a flexure 12 formed of a very thin plate spring fixed to the distal end portion of the beam 11 by laser welding or the like, a base plate 13 fixed to the proximal end portion of the beam 11, etc. The slider 10 is supported by the flexure 12. The load beam 11 has a shape similar to an isosceles triangle, tapered from its proximal end portion toward its distal end portion. A bent edge 14 is formed on each of two opposite oblique side portions of the beam 11.
A hemispherical support projection 15 protrudes from the distal end portion of the load beam 11 toward the flexure 12. As shown in FIG. 11, the distal end of the projection 15 abuts against the flexure 12. Accordingly, the head 8 can make three-dimensional displacements, such as pitching and rolling, around the projection 15. The projection 15 is also called a dimple in the art. The projection 15 may be provided on the flexure 12 in place of the load beam 11.
As modern information processing apparatuses, such as personal computers, are reduced in size, the shock resistance of the HDD becomes a more important factor for the following reasons. In the case of a personal computer that uses a small-sized HDD (2.5-inch HDD), such as a so-called notebook computer, the shock-absorbing capability of its casing is not good enough. In the case of a desktop computer (using a 3.5-inch HDD), on the other hand, the HDD may possibly be subjected to a relatively heavy shock if it is handled wrongly in assembling operation.
When the aforementioned conventional suspension 7 was subjected to a shock exceeding its tolerance limit, the head 8 fluttered, and the head 8 and the disk 9 were damaged. The inventors hereof observed the movement of the shocked head 8 by using a high-speed camera and the like, and found that the head 8 and the disk 9 were damaged in the following manner. When the head 8 was shocked, the distal end of the load beam 11 sprang up, as shown in FIG. 12. Thereupon, the head 8 underwent pitching or rolling so that its corner portions ran against the surface of the disk 9. A phenomenon called dimple separation such that the flexure 12 and the support projection 15 separates from each other, in particular, is a main cause of the head's fluttering.
FIGS. 13 and 14 show results of a shock test on the conventional suspension 7. Test conditions include a duration time of 0.96 msec, acceleration (G's) of 452 G, and contact pressure (G/L) of 3.5 gf between the projection 15 and the flexure 12. As shown in FIG. 13, the respective displacements and moving speeds of the head 8 and the projection 15 increase remarkably at points near 1.0 msec on the axis of abscissa, and there is a time lag between the displacements of the members 8 and 15. This shows the occurrence of dimple separation. As shown in FIG. 14, moreover, the head angle changes drastically at points near 1.0 msec on the axis of abscissa.